>> reporter: turning out, there is a science to getting those priceless reactions. one study found, pricier gifts don't translate into greater appreciation. exhibit one, the kitten. >> oh my god! >> reporter: the key, studies show, is getting into the head of the recipient. and in the head of a kid, this electric guitar is a good idea. experts say you should give the recipient exactly what they say they want, not what you think they should want. >> what the heck is that? that's not toys, that's books! >> reporter: in other words, stick to the list. and reap the rewards. sharyn alfonsi, abc news, new york. >> and thank you for watching. "nightline" will be along later. we leave you tonight with the national christmas tree. 28 feet tall, the lights just switched on. good night. you won't take my life. you won't take our future. aids affects us all. even babies. chevron is working to stop mother-to-child transmission. our employees and their families are part of the fight. and we're winning. at chevron nigeria, we haven't had a reported case in 12 years. aidss strong.